$ \left(\dfrac{5}{6}\right)^{-3}$
Solution: $= \left(\dfrac{6}{5}\right)^{3}$ $= \left(\dfrac{6}{5}\right)\cdot\left(\dfrac{6}{5}\right)\cdot \left(\dfrac{6}{5}\right)$ $= \dfrac{36}{25}\cdot\left(\dfrac{6}{5}\right)$ $= \dfrac{216}{125}$